In the 1×EV-DV system, also sometimes referred to as cdma2000, Release C or Release D, a packet data call does not use the conventional soft handoff process for the forward (base station to mobile station) packet data control channel/packet data channel (F-PDCCH/PDCH), but uses cell selection instead. The reverse (mobile station to base station) Quality Channel Indicator Channel (R-CQICH) is used to report the pilot channel carrier to interference ratio (C/I) information for the current serving sector (currently serving base station), and to indicate cell switching. In order to perform cell selection, the mobile station is required to make C/I measurements of the base stations in its Active Set and to determine whether a change of the serving base station is needed. If a change of serving base stations is needed, the mobile station initiates the base station switching procedure by applying the Walsh cover of the target base station to the C/I measurement and transmitting a distinctive switching pattern on the R-CQICH channel.
In a cellular communications system of interest to this invention the Active Set may contain up to six base stations, and it is possible that all six base stations support packet data service, such as enhanced packet data service, also known as 1×EV-DV. In a case where the mobile station includes six fingers, i.e., six PN (pseudonoise) decorrelators or demodulators, at least two of the fingers may be assigned to multi-paths of the same base station. When a plurality of the fingers are assigned to the same, serving base station, it may become difficult to reliably measure with the remaining finger hardware the C/I of all non-serving base stations in the packet data channel Active Set.
More specifically, since typically two to three multi-paths are observed in the radio channel (per base station), 10 to 15 demodulation elements could be required in order to continuously measure the C/I of five non-serving active base stations. As can be appreciated, this would represent a large amount of complexity in order to implement the C/I measurement function, as compared to the hardware needed to just demodulate the traffic data.
When performing a set maintenance procedure, a conventional function of the mobile station continuously measures the Pilot channels of the Active and Neighbor sets. However, for cell selection the mobile station should measure the average C/I of all base stations in its packet data channel Active Set in order to select the best base station.
It would thus be beneficial to provide a mobile station having reduced hardware complexity, and a means to control the hardware to provide the required C/I measurements for cell selection and 1×EV-DV cell maintenance.